linux-kernel - [PATCH 2/2] x86,efi: Implement no_storage

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Date:	Wed, 10 Apr 2013 10:59:35 +0200
From:	Richard Weinberger <richard@....at>
To:	matt.fleming@...el.com
Cc:	cbouatmailru@...il.com, ccross@...roid.com, keescook@...omium.org,
	tony.luck@...el.com, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org, matthew.garrett@...ula.com,
	Richard Weinberger <richard@....at>
Subject: [PATCH 2/2] x86,efi: Implement no_storage_paranoia parameter

Using this parameter one can disable the storage_size/2 check if
he is really sure that the UEFI does sane gc and fulfills the spec.

This parameter is useful if a devices uses more than 50% of the
storage by default.
The Intel DQSW67 desktop board is such an sucker for exmaple.

Signed-off-by: Richard Weinberger <richard@....at>
---
 arch/x86/platform/efi/efi.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 3f96a48..1b0efb6 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -41,6 +41,7 @@
 #include <linux/io.h>
 #include <linux/reboot.h>
 #include <linux/bcd.h>
+#include <linux/module.h>
 
 #include <asm/setup.h>
 #include <asm/efi.h>
@@ -71,6 +72,13 @@ static efi_system_table_t efi_systab __initdata;
 
 unsigned long x86_efi_facility;
 
+static bool efivars_no_storage_paranoia;
+module_param_named(no_storage_paranoia, efivars_no_storage_paranoia, bool, 0644);
+MODULE_PARM_DESC(no_storage_paranoia, "Use this parameter only if you are very"
+		 " sure that your EFI implemenation does sane garbage"
+		 " collection and fulfills the UEFI spec."
+		 " Otherwise your board may brick."
+		 " See: http://mjg59.dreamwidth.org/#entry-22855");
 /*
  * Returns 1 if 'facility' is enabled, 0 otherwise.
  */
@@ -1023,7 +1031,10 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
 			    " is returning MaxVariableSize=0\n");
 
 	if (!storage_size || size > remaining_size ||
-	    (max_size && size > max_size) ||
+	    (max_size && size > max_size))
+		return EFI_OUT_OF_RESOURCES;
+
+	if (!efivars_no_storage_paranoia &&
 	    (remaining_size - size) < (storage_size / 2))
 		return EFI_OUT_OF_RESOURCES;
 
-- 
1.8.1.4

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